The present invention relates to techniques for presenting visual images of acoustically illuminated objects and more particularly to imaging techniques commonly referred to as B-scan, C-scan and scanned acoustical holography.
Such techniques are presently being utilized in varying degrees for medical diagnosis and for nondestructive testing of optically opaque materials (liquids and solids) in which an acoustical pulse transmitter-receiver is scanned over the material. Generally the images from B-scan and C-scan techniques are displayed on a cathode ray tube (CRT) in two-dimensional form with B-scan display system showing a two dimensional depth cross section (X-Z plane or Y-Z plane) and the C-scan display system showing a two dimensional plan view (X-Y plane). In both systems the elapsed time of the acoustical pulse traveling from the transmitter to the attenuating surface or internal discontinuity back to the receiver and the amplitude of the reflected acoustical signal are measured. Generally the B-scan and C-scan techniques involved; (1) intensity modulation or brightening of the CRT spot in proportion to the amplitude of the reflected signal; (2) deflection of the CRT trace in synchronization of the scan mechanism over the object; (3) progressive production of the CRT image as the object is being scanned by use of long-persistent phosphor.
The visual image produced from both B and C-scan techniques is a flat two dimensional pattern which has the major shortcoming that both spatial and depth information are not displayed on a single record.
To overcome this shortcoming, Mssrs. Becker and Trantow devised a technique for displaying the scanned amplitude and lapsed time information in an isometric or three dimensional image of the object on a CRT. Such "isometric" technique is described in U.S. Pat. No. 3,792,423 granted Feb. 12, 1974. Although such technique is a significant improvement in the imaging of acoustically scanned objects, such images lack surface contouring information of the object or the internal defect and often have degraded surface definition.
One of the principal objects of this invention is to provide an imaging apparatus for visually displaying an isometric image of an acoustically illuminated object in which the isometric image depicts surface contour information and definition.
An additional object of this invention is to provide an improved isometric imaging system in which the view angle of the isometric image may be continuously varied while the image is being displayed with the image continuously depicting surface contour information of the object.
A further object of this invention is to provide a reliable acoustical imaging apparatus capable of providing flicker-free isometric images of objects illuminated with pulsed acoustical energy.
These and other objects and advantages of this invention will become apparent upon reading the following detailed description of a preferred embodiment.